Copending U.S. patent application No. 121,321 discloses a key device combining a common mechanical key and an infrared transmitter incorporated in the handle of the key device. The key device may be used as a remote controller for opening the door of the vehicle and, also, as an electronic code transmitter which is used in combination with the mechanical key as an ignition key of improved security. In such a case, it is advantageous to establish an electric contact between the key device and the corresponding locking cylinder for transmitting electric power from the vehicle to the handle of the key or for exchange of signals between the key device and the locking cylinder. Particularly when the handle of the key device incorporates a transmitter for locking/unlocking the door of the vehicle, the key device must be incorporated with a battery and keeping this battery electrically charged is an important requirement for satisfactory performance thereof.
Japanese Patent Laid Open Publication No. 62-1659 discloses electronic keys which are provided with connectors 18, 20, 40, 42, 52 and 54 which are electrically connected to the corresponding connectors 30, 32, 48, 50, 56 and 58 on the vehicle when the keys are inserted into the corresponding locking cylinders for the purpose of electrically charging the rechargeable batteries for these electronic keys.
However, according to this proposal, the mechanical key is ether unusual in shape or required to be made of electrically insulating material, the user must overcome a very unfamiliar feel, and, therefore, the commercial acceptability of this key structure based on this proposal may not be satisfactory. Further, the disclosure of this Japanese patent publication is limited to a conceptual structure and does not teach anything which assures the reliability of the electric contact between the key and the locking cylinder.
U.S. Pat. No. 4,148,372 discloses a contact structure in its FIGS. 2 and 3 for establishing an electric contact between the key and the locking cylinder. The key is provided with a resistor pellet 16 which serves as an electronic code. The electric contact is required here in order to obtain an electric access to the resistor pellet. According to this proposal, spring loaded contacts 18, 20, 22 and 24 are provided in the rotor for receiving the key, and are used to electrically contact not only the resistor pellet but also a pair of slip rings 26 and 28 provided in a stationary sleeve which surrounds the rotor. As shown in FIG. 1 of this patent, the contact structure is provided at the entrance to the locking cylinder. But, this structure is not suitable for applications where the short-circuiting of the contacts of the locking cylinder is not permitted because, according to the proposed invention, the contacts engage the metallic part of the key shank as it is inserted into the key hole and are electrically connected to each other. Further, each electric path contains two points of sliding contact (between the key shank and the contact engaged thereto, and between the slip ring and the contact engaged thereto), and the electric continuity may therefore not be kept at all time.